This application claims priority to European Patent Application No. 024475250.8, filed Dec. 10, 2002, herein incorporated by reference.
1. Field of the Invention
The present invention relates to a reciprocating slat conveyor according to the preamble of the first claim. The present invention also relates to a slat for use with such a reciprocating slat conveyor.
2. Description of the Related Art
The use of reciprocating conveyors in trucking, waste hauling and shipping industries, where the reciprocating floors are used to load and unload cargo or transported commodities to assist personnel performing the loading or unloading operations, is well known in the art. To accomplish these tasks, the reciprocating conveyor usually comprises a plurality of elongated conveyor slats disposed side-by-side, edge to edge, lengthwise of the conveyor. The slats are divided in groups of three slats and sets of slats. Each group of slats includes a slat from the first set, positioned next to a slat from the second set, which in turn is positioned next to a slat from the third set. The slats of a particular set are driven by a common transverse drive beam, which in turn is connected to a corresponding drive unit. The drive units are operated to move the transverse drive beams with the slats, in unison, over a predetermined stroke length in a first direction, so as to convey a load in that first direction. Thereafter, each drive unit is operated in the opposite direction to retract all slats belonging to a particular set, one set at a time. When moving the slats in unison, over a predetermined stroke length in a first direction, the load carried by the conveyor is moved in that direction. By non-uniformly retracting the slats in a return stroke in groups of three slats, the load remains in place and does not move in the direction of retraction.
From U.S. Pat. No. 6,013,585 a conveyor slat is known, comprising a body of a fibre reinforced thermosetting resin. The slat includes an outer surface portion made of thermoplastic material. The slat is produced by passing a reinforcement fabric, the thermosetting resin and the thermoplastic material through a pulltrusion die with a heated section. The thermoplastic material may be applied for example by adding some thermoplastic material to the thermosetting resin impregnation bath, by spraying on the reinforcing fabric, after it has been soaked with thermosetting resin, by combining thermoplastic fibres with the reinforcing fabric etc. The heating causes the thermoplastic material to melt and to form a thermoplastic surface layer on the slat. Later, this thermoplastic surface layer may be further bonded to a thermoplastic veil.
Conventional slats for use with a reciprocating conveyor are disclosed for example in U.S. Pat. No. 5,447,222 to Foster. The slats disclosed in U.S. Pat. No. 6,019,215 are elongated members formed by the process of extrusion or co-extrusion. Each slat comprises a plank-like upper portion, which in turn is divided into three sections, opposite sides of a centre section being flanked by side portions. At the position where the centre section meets a side portion, each time a leg extends form the lower surface of the upper portion. Each depending leg comprises a bottom flange, the bottom flanges pointing either towards each other, away from each other or in opposite directions. The bottom flanges are provided to engage the guide beam to which the slat is confined, to prevent upward movement of the slat relative to the guide beam. Each plank-like upper portion has a lower bearing surface that is positioned to contact an upper surface of the guide beam to directly and support the slat on the guide beam in a slideable manner.
When driving the slats, the displacement implied to the guide beam is transferred to the slats along the contact surface of the guide beam with the slat. With the slats of U.S. Pat. No. 5,447,222 this means that the driving force implied by the guide beam is transferred to the slats along the bottom flanges and from the upper bearing surface of the guide beam to the lower bearing surface of the plank-like upper portion.
U.S. Pat. No. 5,588,522 relates to a reciprocating conveyor floor for palletised loads. This conveyor floor comprises (i) a plurality of laterally spaced-apart conveyor slats mounted on a support frame for longitudinal reciprocation between xe2x80x9cstartxe2x80x9d and xe2x80x9cadvancedxe2x80x9d positions, and (ii) a plurality of laterally spaced apart holding slats for vertical movement between an xe2x80x9cupxe2x80x9d and a xe2x80x9cdownxe2x80x9d position in which the holding slats are located respectively above and below the conveyor slats, the movement of the holding slats being restricted solely to a vertical movement. With the holding slats in the down position, the conveyor slats support and convey the load as the conveyor slats move from their xe2x80x9cstartxe2x80x9d to their xe2x80x9cadvancedxe2x80x9d position. After the conveyor slats reach their advanced positions, the holding slats are raised to the xe2x80x9cupxe2x80x9d position, thereby lifting the load from the conveyor slats. The holding slats comprise an upper plank-like portion, a centrally depending leg with bottom flanges which are supported and driven by a lifting tube, the centrally disposed leg having a smaller length than the intermediate legs disposed sideways thereof.
There is however a need to a conveyor floor with improved transfer of the driving forces from the drive beam to the slats.